1. Field of the Invention
This invention relates to cast magnetic soft ferrite and a method of producing the same.
2. Prior Art
Magnetic soft ferrite products have been often employed as magnetic recording heads and magnetic cores of various equipments used at high frequency.
The conventional method of producing the magnetic soft ferrite is analogous to that for ceramics. General method of preparation is that a mixture of powdery raw materials of a magnetic soft ferrite or a compound as the starting material is sintered in a furnace at about 1100.degree. to 1400.degree. C. to get a product. At present three kinds of method, the dry method, coprecipitation method and atomization-thermal decomposition method are practical in the preparation of ferrites. According to those methods, it is difficult to exceed a certain limit of bulk density of the ferrite. Fluctuations of each given condition in producing processes exert an aggravating influences on the high frequency characteristics as well as on magnetic properties of the product. It is therefore difficult to provide a stable mass-production of the ferrite products having excellent characteristics.
Some products of magnetic soft ferrite are manufactured by cutting out from monocrystals. This cutting method is also influenced by the fluctuation of monocrystalline composition and segregation. In addition to these problems, this method costs a large expenditure in manufacturing and machining process. For this reason, the magnetic soft ferrite products formed of a monocrystalline material are used only in limited applications such as VTR magnetic heads.
One of the present inventors has invented a magnetic soft ferrite produced by melting and casting the compounds with a general formula such as MO.Fe.sub.2 O.sub.3 (wherein M represents a divalent metal ion) or M'O.sub.0.5.Fe.sub.2.5 O.sub.4 (wherein M' represents a monovalent metal ion) and disclosed it with a method of producing the ferrite (Japanese Patent Application No. 63-289582).
In the first formula given above, for instance, M=Fe and Zn, a compound such as Fe.sub.0.6 Zn.sub.0.4 O.Fe.sub.2 O.sub.3 is useful as a magnetic cores having a good magnetic characteristics, such as a large value of saturation magnetization and large initial permeability. When producing this soft ferrite by melting and casting, however, the inventors often encountered unforeseen difficulties to obtain a product having a desired composition.